Help me in solving AIRM problem

help
,
1

My issue

i have tried to take the whole input in one vector .then calculated the most frequency of the vec . Can anyone tell why it is not passing all the testcase ?

My code

#include <iostream>
#include <bits/stdc++.h>
using namespace std;

int main() {
	// your code goes here
	int t ;
	cin>>t ;
	while(t--){
	    
	   // vector<int> d ;
	   int m = 1 , c =1  ;
	    int n ;
	    cin>>n ;
	    vector<int> a(n*2) ;
	    for(int i=0 ; i<(n*2) ; i++){
	        cin>>a[i];
	    }
	    sort(a.begin(), a.end());
	    for(int i=0 ; i<(n*2) ; i++){
	        if(a[i]==a[i-1]){
	            c++ ;
	        }
	        else {
	            c = 1 ;
	        }
	        if(c>m){
	            m = c ;
	        }
	    }
	    
	    cout<<m<<endl ;
	}
	return 0;
}

Problem Link: AIRM Problem - CodeChef

2

@indrajit_1010
If u are checking for a[i]==a[i-1] then your loop should begin from 1 not 0.